KR910003854B1 - Liquid crystal compounds with 4-(optically active alkyl)-3-cyanophengl groups - Google Patents

Abstract

Optically active liquid crystal compounds and chiral liquid crystal compositions containing them, the compounds having the formula: <CHEM> in which R<1> is C2-C18 alkyl group; R<2> is a C1-C12 alkyl or alkoxy group, a cyano group or a hydrogen or halogen atom; A is a group -COO- or -OCO-; B and C are each a single bond or a group <CHEM> (in which X is a hydrogen or halogen atom or a cyano group); and l , m and n are each 0 or 1.

Description

Liquid Crystal Compound Having 4- (Optically Active Alkyl) -3-Cyanophenyl Group

The present invention relates to a novel liquid crystal compound and a liquid crystal composition containing the same. More particularly, the present invention relates to a liquid crystal compound having an optically active group and a chiral liquid crystal composition containing the same.

TN (twist nematic) display mode is most widely used at present, but this is insufficient in view of the response speed for light emitting display elements such as electroluminescence, plasma display and the like. Therefore, various improvement methods have been tried from this point of view, but its great potential for improvement does not seem to remain that much.

That is, various apparatuses based on other principles have been tried instead of the principle of TN mode display elements, and among them, there are display modes using ferroelectric liquid crystals (NA Clark et al: Applied phys. Lett. 36, 899 (1980)). This mode uses ferroelectric liquid crystal chiral smectic phase C (hereinafter abbreviated as SC ^* phase) or other smectic phases (e.g., SH ^* phase, SF ^* phase, SC ^* phase, etc.) and compares with TN display mode. It has three excellent specific aspects.

The first particular aspect consists in providing a very high response speed, in which this mode is 100 times that of a TN mode display element: in a second, the mode provides a memory effect such that multiple driving is easily combined with the high speed response described above; A third particular embodiment consists in that the gray scale can be obtained more easily than the TN display mode by adjusting only the inversion time of the polarization, so that this mode is considered to be suitable for graph display.

However, despite the fact that this mode has certain specific aspects as described above. Currently known ferroelectric liquid crystals and compositions do not yet provide sufficiently satisfactory results in terms of response speed, so this mode is slightly deadrock before practical use of them. One reason for this is that the development of compounds with large naturally occurring polarization values Ps has been delayed.

It is an object of the present invention to provide a liquid crystal compound having a particular aspect suitable for the display mode, in particular having a large naturally occurring polarization value.

The present inventors have extensively researched to develop an optically active liquid crystal compound suitable for use in the display mode, and as a result, achieve the present invention.

The present invention relates to an optically active liquid crystal compound of formula (I) and a chiral liquid crystal composition containing at least one liquid crystal compound.

또는

(여기서, X는 수소원자, 할로겐원자 또는 시아노 그룹을 나타내며 ; l,m 및 n은 각각 0또는 1을 나타낸다.In the formula, R ¹ represents an alkyl group having 2 to 18 carbon atoms; R ² each represents an alkyl group or alkoxy group, a hydrogen atom, a halogen atom or a cyano group having 1 to 20 carbon atoms; A represents -COO- or -OCO-; B and C are each a single bond,

or

(Wherein X represents a hydrogen atom, a halogen atom or a cyano group; l, m and n each represent 0 or 1).

Representative phase transition points and naturally occurring polarization values Ps of the compounds of general formula (I) of the present invention are shown in Table 1.

TABLE 1

1) Simply extrapolate from the values of Ps of the achiral Sc material and mixtures thereof as illustrated in Examples 6 and 7.

2) Samples 3, 8 and 9 correspond to Examples 3, 1 and 2, respectively.

The first specific embodiment of the compound of general formula (I) is that its naturally occurring polarization value is large. In ferroelectric liquid crystals having a large spontaneous value, it is known that its response speed, i.e., the rate at which molecules are inverted in an electric field, is higher than that of a ferroelectric liquid crystal having a small spontaneous polarization value.

Certain compounds of formula (I) of the present invention have naturally occurring polarization values in excess of about 40 nC / cm ² . On the other hand, in the case of a compound corresponding to the compound of general formula (I) but not having a cyano group (that is, having a hydrogen atom instead of a cyano group), for example, compound (A) ( Sub) 53-22883 / 1978) has about + InC / cm 2 as measured by the inventors.

That is, it was assumed that the large naturally occurring polarization value of the general formula (I) of the present invention is derived from the fact that the cyano group is in the ortho-position with respect to the optically active group. That is, it is contemplated that substituents having a permanent dipole moment perpendicular to the principal axis of the molecule, ie, cyano groups, are in close proximity to the asymmetric carbon atoms, causing large spontaneous polarization by interaction between the two. On the other hand, in the case of a compound having an asymmetric carbon atom separate from the dipole moment of its substituent or a compound having a substituent having a dipole moment much smaller than a cyano group (e.g., fluorine atom, chlorine atom, bromine atom, etc.), its natural occurrence Polarization is not that big. That is, the inventors have found that, for example, in the case of a compound having a fluorine atom instead of the cyano group of the general formula (I) of the present invention, its naturally occurring polarization value is almost absent.

Large spontaneous polarization can be thought to originate from the following nuclei.

또는

및 이러한 핵을 함유하는 액정화합물이 큰 자연발생 분극치를 갖는 우수한 강유전성 액정 물질이다.0-cyano-2-methylalkylphenyl or 0-cyano-1-methylalkylphenyl, these groups corresponding to when l = 0 or 1 in general formula (I),

or

And liquid crystal compounds containing such nuclei are excellent ferroelectric liquid crystal materials having large naturally occurring polarization values.

In particular, compounds with l = 1, ie compounds with O-cyano-2-methylalkylphenyl groups, are easier to prepare than compounds with l = 0; In this respect the former compound is actually more important than the latter. In addition, compounds having an optically active group having an absolute configuration of S-type are advantageous in view of their natural material being available for commercial use.

Of interest is the comparison of a compound of Formula (I) with a cyano-unsubstituted compound of Formula (A). When comparing two classes of compounds that both have an S-type absolute configuration, i, a compound of formula (I) is a minus sign and has a large spontaneous polarization, while a compound of formula (A) is a plus sign Has a small polarization value; ii) Both compounds of formula (I) and compounds of formula (A) have a preferential twist sensation on Smectic C: iii) the compounds of formula (I) and compounds of formula (A) are each nematic Both cholesteric phases induced in addition to liquid crystals have a preferential twist sensation

The fact of (i) is that the cyano group in the phenyl ring-ortho-position has a sign opposite to that of spontaneous polarization based on 2-methylalkylphenyl group and also has a larger spontaneous polarization value than the latter. This can be explained as Furthermore, the fact of (ii) and (iii) above will indicate that the direction of the helical is determined only by the absolute configuration of the optically active group. This particular embodiment of the compound of formula (I) makes the compound useful as a component of the chiral smectic C liquid crystal composition. That is, when the S-type compound of general formula (I) with l = 1 is used together with another SC 'compound having the sign of the naturally-occurring polarization value-, the electronic compound has its spontaneous polarization value unlike the A-type compound. It is possible to provide a large spontaneous polarization value without offsetting, and since its helical direction is preferential, the electronic compound can make the helical pitch of the left linear SC ^* liquid crystal composition longer.

In addition, since the compound of general formula (I) has an optically active carbon; When added to nematic liquid crystals (cholesteric phase), they have the ability to induce twisted structures.

The nematic liquid crystal having a twisted structure, that is, the chiral nematic liquid crystal does not form the inversion zone of the so-called TN mode display element; It is also possible to use compounds as inhibitors of inversion zone formation.

Compounds of formula (I) of the present invention have a particular embodiment of a strong twist force and a temperature-dependency of a small twist force. That is, with respect to the cholesteric pitch of the chiral nematic liquid crystal, for example, when 1% by weight of the compound of Sample No. 8 in Table 1 is added to ZrI-1132 (manufactured by Merck Company), the pitch of the resulting composition is measured. Since it is short as 19 micrometers; They are very useful as pitch-controlling agents for chiral nematic liquid crystal compositions.

In addition, its temperature-dependence is so small that the temperature specific embodiment Sp represented by the following general formula is very small as +0.212 (when t ₁ = 20 and t ₂ = 70 ° C.).

This is, for example, a P of +0.584 when measured under the same conditions for (S) -4- (2'-methylbutyl) -4'-cyanobiphenyl, a currently known pitch-regulator for chiral nematic liquid crystal compositions. It is an amazing aspect compared to having.

Formula (I) compounds are prepared as described below.

Compounds of formula (I) wherein A is -COO- and n is 1 can be prepared according to the following scheme.

In the above scheme, R, ¹ R ² , I, m, B and C are as described above.

That is, 4- (1'-methylalkyl) benzoic acid, 4- (2'-ethylalkyl) benzoic acid, 4- (1'-methylalkyl) biphenyl-4'-carboxylic acid or 4- (2'-methylalkyl) Brominated biphenyl-4'-carboxylic acid (1) in the presence of a catalyst to give 3-bromo-4- (1'-methylalkyl) benzoic acid, 3-bromo-4- (2'-methylalkyl) benzoic acid, 3 After -bromo-4- (1'-methylalkyl) biphenyl-4'-carboxylic acid or 3-bromo-4- (2'-methylalkyl) biphenyl-4'-carboxylic acid (2) The resulting compound is esterified by reacting with a phenolic compound to produce compound (3), and the compound is reacted with a cyanoating agent such as copper cyanide to prepare a compound of formula (I).

In the reaction step, the cyanoation reaction and the esterification reaction may be reversed in order. That is, compound (2) is cyanoated to give 3-cyano-4- (1'-methylalkyl) benzoic acid, 3-cyano-4- (2'-methylalkyl) benzoic acid, 3-cyano-4 (1 '-Methylalkyl) biphenyl-4'-carboxylic acid or 3-cyano-4- (2'-ethylalkyl) biphenyl-4'-carboxylic acid is produced and the resulting compound is esterified to yield ) Can be prepared.

Compounds of formula (I) wherein A is -OCO- and n is 1 can be prepared according to the following scheme:

In the above scheme, R ¹ , R ² , I, m, B and C are as described above.

Even in the reaction step. The order of the cyanoation reaction and the esterification reaction can be reversed. That is, compound (7) is cyanoated to give 3-cyano-4- (1'-methylalkylphenol, 3-cyano-4- (2'-methylalkyl) phenol, 3-cyano-4- (1 '-Methylalkyl) -4'-hydroxybiphenyl or 3-cyano-4- (2'-methylalkyl) -4'-hydroxyhydroxyphenyl is produced, followed by esterification of the resulting compound The compound of (I) can be prepared.

Compounds of formula (1) wherein n is 0 and B and C each represent a single bond can be prepared according to the following scheme:

When R ² is alkoxy

R ', I and m in the above scheme are as described above; R is an alkyl group

That is, the compound (7) prepared above is reacted with an alginating agent such as alkyl bromide to produce a compound (9), and the compound is reacted with a cyanoating agent such as copper cyanide, to give the compound of formula (1). To prepare.

When R ² is alkoxy

Wherein R ', I and -m are as described above; R is an alkyl group.

That is, 4- (1'-methylalkyl) -alkylbenzene, 4- (2'-methylalkyl) -alkylbenzene, 4- (1'-methylalkyl) -4'-alkylbiphenyl or 4- (2 ' -Methylalkyl) -4'-alkylbiphenyl (10) is brominated in the presence of a catalyst to give compound (11), which is reacted with a cyanoating agent, such as copper cyanide, to give the compound of formula (I) To prepare.

The optically active liquid crystal compound according to the present invention will be described in detail by the following examples.

Example 1

인 일반식(I)의 화합물(화합물번호8)]의 제조(s) -3-cyano-4- (2'-methylbutyl) benzoic acid 4-octyloxy-4'-biphenylyl ester [m = 0; n = l; A = -COO-; R1 = C2G5-; R2 = -IC8H17; And B = C =

Preparation of Phosphorus General Formula (I) (Compound No. 8)]

A solution of silver nitrate (177 g, 1.1 mol) in water (500 ml) was dissolved in (s) -4- (2'-methylbutyl) benzoic acid (200 g, 1.0 mol), nitric acid (680 ml) and bromine (in water (500 ml)). 183 g, 1.1 mol) of the mixture was added dropwise under ice-cooling, and then the mixture was stirred at room temperature for 5 hours and poured into ice water. The precipitated crystals are filtered off and 10% aqueous sodium carbonate solution (2 l) is added, then the mixture is sufficiently stirred and the remaining insoluble material is filtered off. The filtrate was acidified with sulfuric acid and the precipitated crystals were filtered and then recrystallized with acetic acid (1 L) to give 3-bromo-4- (2'-methylbutyl) benzoic acid (106.0 g; melting point; 78.8 to 79 .7 '). C) is obtained.

Thionyl chloride (118 g) was added to 3-bromo-4- (2'-methylbutyl) benzoic acid (100 g, 0.37 mol) and the resulting mixture was refluxed for 2 hours, after which excess thionyl chloride was removed under reduced pressure. Distillation to afford 3-bromo-4- (2'-methylbutyl) benzoic acid chloride (I05.lg).

The prepared 3-bromo-4- (2'-methylbutyl) benzoic acid chloride (11.5 g, 0.04 moles) was added dropwise by ice-cooling to a mixture of 4-hydroxy-4'-octyloxybiphenyl and anhydrous pyridine. The resulting mixture is stirred at 50-60 ° C. for 2 hours, then toluene (100 ml) is added. The mixture is stirred well and washed with 6N-HCl, then in 2N-NaOH aqueous solution, washed again with water and dried over anhydrous MgSO ₄ . Toluene was distilled off and the residue was recrystallized from a mixture of ethanol (100 ml) and ethyl acetate (60 ml) to give 3-bromo-4- (2'-metalbutyl) benzoic acid 4'-octyloxy-4-biphenylyl ester ( 12.2 g) is obtained. This compound exhibits liquid crystal characteristics and its phase transition point is as follows.

3-Bromo-4- (2'-methylbutyl) benzoic acid 4-octyloxy-4'-biphenylyl ester (5.5 g, 0.01 mol), cuprous cyanide (1.1 g, 0.06 mol) and dimethyl The mixture of formamide (20 ml) was heated to 145-147 ° C. and stirred for 6 hours, after which a mixture of ferrous chloride (4 g), hydrochloric acid (1 ml) and water (7 ml) was added. The mixture is kept at 60 to 70 ° C. for 15 minutes, added to ice water, toluene is added, and the mixture is thoroughly stirred and transferred to a separating funnel. The resulting organic layer was washed several times with water and dried over anhydrous MgSO ₄ , then toluene was distilled off and the residue was recrystallized from ethanol (50 ml) to give the desired 3-cyano-4- (2'-methylbutyl) benzoic acid 4 '. Obtain octyloxy-4-biphenylyl ester (1.7 g).

The phase transition points of this product are as follows.

Example 2

인 일반식(Ⅰ)의 화합물(화합물번호 9)]의 제조(S) -3-Sano-4- (2'-methylbutyl) benzoic acid 4'-decyloxy-4-biphenylyl ester [m = 0: n = 1: A = -COO-: R ¹ = C ₂ H ₅ ; R ² = OC ₁₀ H ₂₁ ; And B = C =

Preparation of Phosphorus General Formula (I) (Compound No. 9)]

Example 1 was repeated, except using 4-hydroxy-4'-decyloxybiphenal instead of 4-hydroxy-4'-octyloxybiphenyl, (S) -3-cyano-4 Obtain-(2'-methylbutyl) benzoic acid 4'-decyloxy-4-biphenylyl ester. The phase transition points of this product are as follows.

Example 3

인 일반식(Ⅰ)의 화합물(화합물번호 4)]의 제조(S) -3-cyano-4- (2'-methylbutyl) banzoic acid 4-octyl-4'-biphenylyl ester [m = 0: n = 1: A = -COO-; R ¹ = C ₂ H ₅ ; R ² = C ₈ H ₁₇ ; And B = C =

Preparation of Phosphorus General Formula (I) (Compound No. 4)]

Example 1 was repeated, except that 4-hydroxy-4'-octylbiphenyl was used instead of 4-hydroxy-4'-octyloxybiphenyl, and (S) -3-cyano-4'- (2'-Methyloctyl) benzoic acid 4'-octyl-4-biphenylyl ester is obtained. The phase transition points of this product are as follows.

As mentioned above, when the order of the cyanoation reaction and the esterification reaction is reversed, Examples 1 to 3 are modified as follows: 3-bromo-4- (2'-methylbutyl) benzoic acid is first cyanoated to 3-cyano-4- (2'-methylbutyl) benzoic acid is first cyanoated to yield 3-cyano-4- (2'-methylbutyl) benzoic acid (melting point 91.2-92.1 ° C.) and then esterified. . The physical properties of the product are the same as in Examples 1-3.

Example 4

및 C=단일결합인 일반식(Ⅰ)의 화합물(화합물번호 17)]의 제조(S) -Cyno-4- (2'-methylbutyl) biphenyl-4'-carboxylic acid 4-octyloxyphenylester [m = 1: n = 1: A = -COO-: R ¹ = C ₂ H ₅ ; R 2 = -OC ₈ H ₁₇ ; And B =

And C = compound of formula (I) having a single bond (Compound No. 17)]

Example 1 was repeated but using (S) -4- (2'-methylbutyl) biphenyl-4'-carboxylic acid instead of (S) -4- (2'-methylbutyl) benzoic acid, S) -3-cyano-4- (2'-methylbutyl) biphenyl-4'-carboxylic acid 4-octyloxyphenyl ester is obtained. The phase transitions of this product are as follows:

Example 5 (Application Example 1)

A liquid crystal mixture composed of the achiral smectic liquid crystal compound in the following ratio is prepared.

The mixture has a melting point of 4 ° C, exhibits an SC phase at higher temperatures, an SA phase at 65 ° C, an N phase at 79 ° C and an isotropic liquid at 90 ° C.

Compound No. 8 (20% by weight) shown in Table 1 was added to the liquid crystal mixture (80% by weight) to prepare a chiral smectic liquid crystal composition.

The liquid crystal composition was coated with a PVC (polyvinyl alcohol) on the surface, and the resulting surface was rubbed into a 2 占 퐉 thick battery equipped with a transparent electrode obtained by rubbing the surface to form a parallel alingning treatment. Place between the polarizer and the analyzer that are staggered and apply a voltage of 15V. As a result, the change in intensity of transmitted light is measured. At this time, when the reaction time is measured from the change in intensity of transmitted light, it is about 125 μsec at 25 ° C.

The composition has a melting point of 0 ° C, exhibits an SC phase at higher temperatures, an SA phase at 69.2 ° C, a cholesteric phase (Ch phase) at 84.5 ° C, and an isotropic liquid at 92.6 ° C. The twist sensations on the SC ^* and Ch phases are both priorities.

In addition, the -3nC / ㎠ at 25 ℃ spontaneous polarization value of the composition is a tilt angle 19 ^o.

As described above, when the compound of formula (I) according to the present invention is mixed with a non-optically active liquid crystal compound, an excellent ferroelectric chiral smectic liquid crystal composition is obtained.

Example 6 (Application Example)

To the same achiral liquid crystal composition (80 wt%) as in Example 5 was added Compound No. 17 (20 wt%) which is a compound according to the present invention. The resulting liquid composition exhibits the following phase transition points.

C-SC ^* 3 ° C, SC ^* -SA 70.0 ° C SA -Ch 80.0 ° C and Ch-I90.6 ° C

In addition, the composition has a naturally occurring polarization value of −4.2 nC / cm ² , an inclination angle of 25 ^° , an SC ^* twist sensation of priority, and a reaction time of 120 μSEC under the same conditions as in Example 5.

Since compound number 17 crystallizes before cooling to the temperature where SC ^* phase appears, it is impossible to directly observe its single SC ^* phase. However, as shown in this example, by mixing the SC liquid crystal composition with compound No. 4, this is useful for constructing the ferroelectric liquid crystal composition. This also applies to the other compounds described in Table 1, which alone do not exhibit the SC ^* phase.

Example 7 (Application Example 3)

A chiral smectic composition was prepared by adding compound No. 3 (described in Table 1) (20 wt%) to the achiral smectic liquid crystal adjuster described in Example 5. This adjustment exhibits the following phase transition points:

C-SC ^* -11 ° C; SC ^* -SA 62.1 ° C; SA-Ch 77.5 ° C; And Ch-1 86.1 ° C.

The spontaneous polarization value of this composition is -6.0 nC / cm 2 at 25 ° C. and an inclination angle of 18 ^° .

It was 90 microseconds as a result of measuring this liquid seed composition as a liquid crystal battery as in Example 5, and measuring reaction time on the same conditions (a voltage is set to 20V).

Example 8 (Application Example 4)

A nematic liquid crystal composition composed of the following components was filled in a battery having a distance of 10 μm between electrodes to make a TN mode display cell, and then observed with a polarization microscope.

As a result, a reverse domain was formed. In addition, the battery used was obtained by coating the surface with polyvinyl alcohol and rubbing the surface to perform parallel alignment.

As described above, compound No. 8 (0.1% by weight) described in Table 1 was added to the nematic liquid crystal composition to prepare the same TN mode battery as described above. As a result of cell observation, the inversion zone was released and a nematic phase appeared.

Claims (8)

Optically active liquid crystal compound of general formula (I).

In the formula, R ₁ represents an alkyl group having 2 to 18 carbon atoms; R ₂ each represents an alkyl group or alkoxy group having 1 to 20 carbon atoms, a hydrogen atom, a halogen atom or a cyano group; A represents -COO- or -OCO-; B and C are each a single bond,

or

(Wherein X represents a hydrogen atom, a halogen atom or a cyano group); l, m and n represent 0 or 1, respectively. The compound of claim 1, wherein R ¹ represents an alkyl group having 2 to 6 carbon atoms; R ² each represents an alkyl group or alkoxy group having 1 to 12 carbon atoms or a hydrogen atom; A represents a -COO- group; B and C are each a single bond,

or

(Where X represents a hydrogen atom or a halogen atom), wherein B and C are not both single bonds; both l and m represent 1; n represents 0 or 1; Optically active liquid crystal compound having a total number of 6-membered rings of 2 or 3 The optically active liquid crystal compound according to claim 1, wherein R ¹ represents C ₂ H ₅ . The compound of claim 2 wherein -BC is

or

Optically active liquid crystal compound showing. A liquid crystal composition containing two or more components, at least one of which is an optically active liquid crystal compound according to claim 1. The liquid crystal composition according to claim 5, wherein the liquid crystal composition exhibits a chiral smear C phase. The liquid crystal composition according to claim 5, wherein the liquid crystal composition exhibits a chiral nematic phase. A light-switching element containing a liquid crystal composition exhibiting a chiral smectic C phase according to claim 6.